Railway crossing signal systems



Jan. 10, 1967 Filed Jan. 21, 1965 IXX IN VEN TOR NORMAN RIDLEY SHAW United States Patent 3,297,868 RAILWAY CROSSING SlGNAL SYSTEMS Norman Ridley haw, 717 66th Ave. SW., Calgary, Alberta, Canada Filed Jan. 21, 1963, Ser. No. 252,855 2 Claims. (Cl. 246-425) The invention is related to a new method of transmitting radio signals from moving railway vehicles to rail-and-road crossings.

In the drawing FIGURE 1 is a plan showing the operation of the principle of the dual overlap transmitting system.

One of the most difficult traflic safety problems is that of unprotected rail-and-road crossings. The only protection for most of the crossings is the road sign, the white railway crossing sign on the pole, and the whistle and the light of the locomotive. Wig-wags and/or flashing lights that are activated by mechanical means are in use at some crossings but these are very expensive so that it has been the practice to use them only at a small number of busy crossings. Under conditions such as bright sunrise or sunset, and in storms of dust, snow, rain and of windshield icing, etc., it is often impossible to see a signal at all. Also, many crossings do not have a clear view for a sufficient distance for a crossing to be seen in time. The answer to this problem is to have a good flashing light and/or an audible signal in the auto, which will warn him when a locomotive is within risk of collision.

The best method I know of to operate such a signal is by means of a radio signal from the locomotive when it is within risk of collision. One method of sending such a signal is described in Canadian Patent Number 344,182 August 28, 1934, Sommer, Class 250-2. However, this method has never been used because, altho the basic idea was sound the method of putting it into practice was not practical. The most serious defect in the system described by Sommer is the lack of a method to control the effective range of the transmitter. He speaks of a range of a few miles. In actual practice, a minimum range of one-quarter mile is required to give the proper warning to the operator of a vehicle. But if the maximum range goes over about a mile receivers will be triggered too far away from the crossing. I have found that signals vary under varying conditions of terrain, atmosphere weather, etc., and to overcome these variations it is necessary to have a controlled beam which has sufficient power to overcome varying local or general conditions but which will have a definite limit on the effective range, so that the signal will not over-reach beyond a certain distance between the locomotive and the vehicle.

The best way I have found to produce a controlled signal is to use a multi-channel transmitter with a range of not less than one mile under the worst conditions and not more than ten miles under the best conditions. At each crossing there is a receiver, turned on idle (warmed up and ready to receive), tuned to receive only one of the ten tones or modulating frequencies that the transmitter can send. These crossing receivers are in a series tone A at the first, tone B at the second and so on to tone K at the tenth receiver. As the locomotive comes within a certain distance of the first crossing (tone A) the transmitter sends a signal in tone A which is picked, up by the receiver at A but is ignored by the receivers B to K and is not strong enough to reach the next A receiver which follows K to start a new series.

The control to operate the signal from the transmitter can be manual for the above described method but under actual operating conditions it is essential to have an automatic control system which requires little or no atten- Patented Jan. 10, 1967 tion from the engineer. The automatic apparatus which operates the multi-channel transmitter to change the tones at exact intervals of distance travelled by the locomotive is activated by the speedometer drive on the locomotive and is set manually at a marker mile 0) at the start of the run. At regular intervals (25 to 50 miles) there will be check markers to show the engineer thru an indicator on the dash if the tone switching control is getting out of synchronization with the mileage and any deviation can be adjusted. On the return run along the same line there is no problem of synchronizing the tone signals from the transmitter with the tone of each receiver as it comes up in the series. All that has to be done is to set the automatic control at the right mileage at the start of the return run and set it to operate in the reverse of the way it operated on the out run.

For manual operation the transmitter is sending only one tone at a time but for the automatic operation it is necessary to switch tones at exact intervals of mileage and with a single tone there would be some crossings which would be too close to the locomotive when the signal is turned on. I have found that a two-tone overlap signal takes care of this problem so that no receiver receives its signal at less than about one-half mile. To illustrate how this works on a sample ten-mile section of railway track, we start at mile 0 and mark off exact one-mile intervals 1 to 10. Then we show the crossings marked with a letter to show the tone of the receiver at that crossing and a number to show the distance in tenths of a mile from the last switch point.

In the drawing which illustrates an embodiment of the invention, FIGURE 1 is a sketch plan of a section of railway showing switch points number 0 to number 10 and eight crossings number A6 to number J8, and the operation of the overlapping tones by letter A to letter At mile 0 the tone control turns on tone A which activates the receiver at A6 which turns on the flashing light on the pole and turns on the secondary transmitter on the pole to send a signal to vehicle.

At mile 1 tone B is turned on and activates the receiver at B2 turning on light and vehicle signal. Tone A is still holding on at signal A6.

At mile 2 tone C is turned on and activates C4. Tone B is still holding signal at B2. Tone A is turned off turning off signal at A6.

At mile 3 tone D comes on but there is no D receiver.

Tone C is holding at C4. Tone B is turned oiT.

At mile 4 tone E comes on and activates E5. Tone D is still on. Tone C is turned off.

At mile 5 tone F comes on and activates F6. Tone E is still holding at E5. Tone D is turned off.

At mile 6 tone G comes on and activates G7. Tone F is still holding at P6. Tone E is turned ofl".

At mile 7 tone H comes on but there is no H receiver.

Tone G is still holding at G7.

At mile 8 tone J comes on and activates the signals at I; and J8. Tone H is still on. Tone G is turned 0 At mile 9 tone K comes on. Tone J is still holding at J6 and at J8. Tone H is turned ofi.

At mile 10 tone A comes on to start the series over again.

In this system the principal function of the crossing signal is to activate an attached transmitter which will send out a signal on the vehicle frequency (secondary) which signal is adapted to the conditions at the particular crossing.

However, there is a signal light also activated by the crossing signal and the principal function of this light is to provide a back-up signal to the vehicle approaching the crossing so that in case of instrument failure in the vehicle the operator will still have a warning if he approaches a crossing in risk of collision. Of course the flashing light at the pole gives good protection to auto vehicles not equipped with a receiver signal but this is an added value to the signal in equipped vehicles.

Embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows;

1. In railway crossing signal systems a multi-channel radio transmitter on a locomotive and a single channel radio receiver set at each crossing said receivers being tuned to each receive only one of the several tones or frequencies which can be selectively transmitted said receivers being arranged in a definite progressive order with regard to the tone of each receiver so that the operator at the locomotive can activate the receiver at the next up-coming crossing without activating the next several receivers which are tuned to receive only in the other tones.

2. The system as claimed in claim 1 together with an automatic control to change transmitter tones at exact intervals of distance so that two tones are on signal all the time and these tones are changed in proper order to provide an overlap of two tones and so turn on and off the receivers in the proper order and at the proper distance.

References Cited by the Examiner UNITED STATES PATENTS ARTHUR L. LA POINT, Primary Examiner.

LEO QUACKENBUSH, Examiner.

S. B. GREEN, Assistant Examiner. 

1. IN RAILWAY CROSSING SIGNAL SYSTEMS A MULTI-CHANNEL RADIO TRANSMITTER ON A LOCOMOTIVE AND A SIGNAL CHANNEL RADIO RECEIVER SET AT EACH CROSSING SAID RECEIVERS BEING TUNED TO EACH RECEIVE ONLY ONE OF THE SEVERAL TONES OR FREQUENCIES WHICH CAN BE SELECTIVELY TRANSMITTED SAID RECEIVERS BEING ARRANGED IN A DEFINITE PROGRESSIVE ORDER WITH REGARD TO THE TONE OF EACH RECEIVER SO THAT THE OPERATOR AT THE LOCOMOTIVE CAN ACTIVATE THE RECEIVER AT THE NEXT UP-COMING CROSSING WITHOUT ACTIVATING THE NEXT SEVERAL RECEIVERS WHICH ARE TUNED TO RECEIVE ONLY IN THE OTHER TONES. 